1. Field of the Invention
The present invention generally relates to IP transport protocols which provide transport functions to internet and other applications. More specifically, the present invention involves implementation of transport layer functions which include multi-homing. The preferred embodiment relates to an extended implementation of Stream Control Transmission Protocol (hereinafter “SCTP”).
2. Background of the Invention
SCTP is an IP transport protocol existing at an equivalent level to UDP (User Datagram Protocol) and TCP (Transmission Control Protocol). SCTP provides a reliable transport service which makes an effort to ensure that data is transported across a network without error and in sequence. SCTP is a connection oriented mechanism which insures that a relationship (or “association”) is created between the endpoints of the session prior to the transmission of data and this relationship is maintained until all data transmission has been successfully completed.
One core feature of SCTP is “multi-homing” or the ability for a single SCTP endpoint to support multiple IP addresses. Among other features, multi-homing provides greater survivability of a session in the presence of network failures. In a single-homed session, the failure of a local LAN access can isolate the end system. With a “multi-homed” session, redundant LAN's can be used to reinforce local access. In a single-homed session, failures within the core network can cause temporary unavailability of transport until the IP routing protocols can reconverge around the point of failure. In a multi-homed session, various options are possible in the core network to reduce the dependency of failures for different addresses. For example, routing may be forced through different carriers by use of addresses with different prefixes. If there is control over the network architecture and protocols, route-pinning techniques or even redundant core networks can be used.
While the teachings of this disclosure may apply to any transmission control protocol and may be more easily applied to a transmission control protocol which supports multi-homing, they are preferably used with SCTP. Information regarding SCTP may be found at www.sctp.org and particularly the Request for Comments publication (“RFC”) for the proposed SCTP standard (RFC 2960 dated October 2000) may be found at http://www.ietf.org/rfc/rfc2960.txt. These disclosures are incorporated herein by reference.